Hey, here is some bitter justice for the 95-99 guys. If they are careful removing their stock .750 stovepipes, so they don't distort them, they can ultimately cut the old pipe up as a sleeve for the new Dorman upper after using it to drive their rd pipe down into the LIM bore.
Yipes! This gives me another idea. We can make an insulating stovepipe with the Dorman as the inner and a thin .750 as the outer that would not have to be epoxied at all! Like the double and triple walled stovepipes for wood burning fireplaces.
So we attach the heat shield to the pipe, not the upper. OK, what'* wrong with this idea?
The spacer at the bottom and the heat shield would need to be a little higher up for the 99+, and we would want the spacer material to conduct heat so the LIM could still provide cooling, but the idea for the .625 LIM bore is basically the same.
If we go with a built-up pipe and shield it might be necessary to give up some of the gap to get a .035" outer wall that is strong enough to drive the unit into the hole - even so, that would leave us with .085".
Probably in production, in would not be that expensive to either CNC these from 6300 aluminum in one piece or fuse the bottom parts so the pipe could be easily installed without separating the parts as they are driven into the hole.
So, what have I overlooked here at 2 in the morning?
Here'* for the 99+. This works easier as a built-up for driving into the LIM bore.
This design will work for the earlier .750 bores by simply pressing the ring on the bottom that I have already tested.
3:30 AM ugh! must sleep.
[edit: It would be good to find an insulating material that could be used for the spacer (not the "washer") in the above image. In fact, if we could find a super insulator like they use for space shuttle tiles, it could be used to fill the gap instead of the oily carbon gunk that the engine will provide. But, as Bob Dillon pointed out to me, when the engine is running, the gap area is likely to exist as a partial vacuum, and a vacuum makes an excellent insulator. Just have to keep it open for the best results. Maybe check and clean the gap every 50,000 miles, like a spark plug....hmmm]